Matching Golf Clubs by MOI

Matching Golf Clubs by Moment of Inertia – a Replacement for Swingweight

Now that TWGT has made it possible for clubmakers to offer matching of clubs to their Moment of Inertia (MOI) as an alternative to swingweight matching, we have received a lot of questions about what MOI matching is and how it can offer clubmakers a better way to build clubs that truly are matched to each other and identical in swing feel. As of 2011, more than 500 custom clubmakers now offer their golfers the shot consistency improvement benefits of MOI matching.

What is MOI Matching?

The MOI of any object is a measurement of its resistance to being put in motion around a defined axis of rotation. Related to golf clubs, if each club in a set requires a different amount of force to swing the club (swinging the club to rotate around our body), the golfer cannot be as consistent swinging each different club in the set. In most simple form, MOI matching scientifically makes each club require the same amount of effort to swing.  This is what makes MOI matched clubs offer better shotmaking consistency than swingweight matched clubs. Swingweight matching does not make each club the same in terms of the amount of force required by the golfer to swing each club and hit the shot. MOI matching does. However, because golfers can be quite different in their strength, tempo and swing mechanics, the right MOI must be identified and custom fit for each golfer to allow the concept to properly work.

Is MOI Matching a new high-tech clubmaking concept?

Not at all.  Back in the 1920s when swingweight was developed, its originators were aware of the principles of MOI matching and tried to make swingweight matching of clubs simulate MOI Matching. They failed because the principle of the swingweight scale they developed could not truly accomplish the task of measuring the MOI of a golf club. Over the decades since the development of swingweight, engineers familiar with the principles of MOI have been in agreement that MOI matching would truly make all clubs within a set swing with exactly the same feel, while swingweight matching could not.

Has MOI Matching ever been done previously in golf clubs?

Yes, there were two previous times in golf equipment history in which companies attempted to offer MOI matched golf clubs. In the 1970s, a company named Sounder Golf offered sets of woods and irons which claimed to be matched by weighting the clubs at specific points within the shaft. The Sounder clubs never caught on for two reasons: 1) Sounder was under-capitalized and unable to generate enough demand through their marketing programs. 2) Every set of Sounder clubs was built to only one specific MOI. Because golfers are different in strength, tempo and swing mechanics, one MOI measurement could never fit the MOI requirements of each golfer.

In the late 1990s, Tommy Armour Golf Company introduced their EQL model clubs to the market. By making all of the woods the same length and same total weight as the 5-wood, and all of the irons the same length/total weight as the 6-iron, the company did achieve a true MOI match for all the clubs within each segment of the set. This concept failed for two reasons; first, because the one MOI measurement to which all the EQL woods and irons were built did not fit all golfers, and second, because the concept of all woods and all irons being the same length was much too radical for golfers to accept.

“About 10 days ago, I received my new Wishon Golf irons with Series 5, R-flex shafts.
My clubmaker, Frank Grasso of Golf Tec, in New Jersey, made up three demo 5-irons and I selected the one with the R-flex shaft. He then made up the set MOI matching the irons. I am happy to report that I am hitting my irons more accurate and consistent than I ever have. I am still experimenting with ball position and yardages, but the MOI matched Wishon irons are a great improvement.

“So far 90% of my misses are 2-3 yards short, where I can get up and down and save pars, as opposed to my old misses which were in bunkers or across cartpaths and almost never getting up and down. These irons are also sneaky long… sometimes it feels like I missed the shot and it ends up perfect. As for the MOI matching, every club in the set plays and feels the same and are effortless to swing. 4 weeks ago, I was ready to take a break from golf, and now, thanks to my new Wishon MOI matched irons, I can’t wait to get to the course to play or practice.”

– Thanks and keep up the good work, Mike Hayes

How is the right MOI determined for each golfer?

Virtually all golfers who play frequently may have noticed they have a “favorite club” or clubs within their current set, or within a previous set of clubs. A “favorite club” may be defined as a club with which the golfer is most consistent over all others, and which the golfer has the utmost confidence in their ability to hit the ball solid and on-center more often than the other clubs in the set. After research and testing, TWGT believes that a one reason golfers have “favorite clubs” is that the MOI of those clubs happens to match the strength, tempo and swing mechanics of the golfer noticeably better than the MOI of other clubs.
There are two ways clubmakers can find the right MOI for any golfer. One is to ask the golfer to bring forth a “favorite club” from any set they may own or have used. The “favorite club” is measured for its MOI using the TWGT MOI Matching System, after which the other clubs are then built to match the MOI of that “favorite club(s)”.

The most common method used by clubmakers is to build a test club(s) based on the fitting recommendations made for the golfer after going through the entire fitting process. By manipulating the headweight of the test club with lead tape, it is possible to find a headweight to “rest of the club” ratio that will result in more comfort for the golfer and a higher percentage of on center hits. Once done, the test club is measured for its MOI, and the TWGT MOI Matching System is used to guide the clubmaker in building all the other clubs in the set to have the same MOI.

Does MOI Matching change the fitting process for the golfer?

No. MOI Matching is simply a replacement for swingweight matching in the fitting process. Clubmakers will fit golfers for every one of the other key fitting specifications based on the same fitting procedures that they have developed and with which they are experienced. Once all of the fitting specifications are determined by the clubmaker, then MOI Matching is brought in to guide the clubmaker in how the clubs will be assembled with regard to final headweight, and in some cases, the final length adjustments.

Is there any aspect of the fitting or performance of the shafts that is changed by MOI Matching?

Very rarely, if ever. As we said, the selection of the shaft is made on the basis of the same fitting procedures the clubmaker is comfortable with using to identify the best shaft for the golfer’s swing speed and swing characteristics of the downswing transition, downswing tempo/acceleration and wrist-cock release.

Because of the final head weighting requirements of the MOI Match for each club, the frequency progression of the shafts will be slightly different than if the clubs were swingweight matched.  In all of our testing, and in the reports of actual MOI fittings that clubmakers have done, we have yet to hear of one case in which the golfer required an adjustment in the tip trimming to offset the different progression of frequency from shaft to shaft within the set that came from the MOI matching headweight requirements. In short, 99% of the time we believe the MOI matching will not affect the golfer’s perception of the shaft fitting.

What will a golfer notice when switching from swingweighted to MOI matched clubs?

We have yet to hear from a clubmaker using the MOI matching system that a golfer for whom MOI matching was performed did not notice a difference in the swing feel of all of the clubs in the set, and a minor to significant increase in the percentage of solid, on-center hits with their clubs. If the golfer “waggles” each MOI matched club, providing they are sensitive to the weight feel of each club, they will detect a progressively increasing headweight feel as the clubs get shorter in the set. But as soon as the clubs are swung full, the golfers all report that they can close their eyes, switch clubs in the set, and not really detect any difference in the total swing feel of the clubs from each other.

If I take a set of MOI matched clubs and measure each club on a swingweight scale, what will I see?

Depending on the MOI each club is made to possess, the swingweight of the clubs in an MOI matched set will very slightly increase from the longest club in the set to the shortest. Most typical is to see the swingweight increase by 0.5 swingweight points per club down through the set.  This is very definitely one of the main reasons golfers like the swing feel of their MOI Matched clubs and do experience an improvement in shot consistency.

Will the woods and irons all be built to have the same single MOI?

No. TWGT testing and feedback from many of the clubmakers using MOI matching in their work has proven that because woods and irons are so different in their length ranges, better results are obtained by matching all the woods to one MOI, and then matching all of the irons to another MOI, with both chosen specifically for each golfer either on the basis of the “favorite club” or the “test club” approach.  The difference in MOI measurement between the woods and irons typically is for the woods to be 50 g/cm2 higher in MOI than the irons.

What about the wedges – should they be built to have the same MOI as all of the rest of the irons?

Again, this was another aspect of MOI fitting and matching that TWGT has spent some time investigating. What we found was that any of the wedges that are chiefly used by the golfer for less than a full swing, it should not be matched to the same MOI as the rest of the irons, each which are predominantly used with a full swing. In general, because many golfers do use the PW and AW (gap wedge) for full swings more than they do the SW and LW, it is OK to make the MOI of the PW and AW the same as the rest of the numbered irons. But for the SW and LW, they are better off being built individually to an MOI or swingweight based on the principles taught in the book, Common Sense Clubfitting: The Wishon Method.

How does the TWGT MOI Matching System work?

In 2006, TWGT introduced an upgrade to the original MOI Matching system with the MOI Speed Match System. This system consists of an electronic device that directly measures the MOI of any golf club in one operation. The older MOI Matching system required clubmakers to manually measure 4 different specifications of each club and then use the accompanying software to calculate the MOI of each club. Thus, the MOI Speed Match hardware is much faster to use to quickly measure the MOI of any club.